Hypoxic/ischemic neonatal brain injury is a major cause of learning disabilities, cerebral palsy, epilepsy and death. The development of neuroprotective strategies to combat this problem requires a greater understanding of the mechanism of neuroprotection. The goal of this research proposal is to determine the molecular mechanism(s) underlying the neuroprotective action of acidic fibroblast growth factor (FGF-1) and scatter factor/hepatocyte growth factor (SF/HGF) against hypoxic/ischemic injury in neonatal brain. In Aim 1, we will use complementary in vitro and in vivo models to determine the relative roles of NMDA and AMPA receptor-mediated excitotoxicity in hypoxic/ischemic injury, and its protection by FGF-1 and SF/HGF. Results will establish the relationship between the extent of brain injury and NMDA and AMPA receptor-mediated excitotoxicity triggered by hypoxia/ischemia, selective neuronal vulnerability to hypoxia/ischemia, and excitatory amino acid receptor-specific mechanism of FGF-1 and SF/HGF protection in neonatal brain. Effects of FGF-1 and SF/HGF on NMDA and AMPA receptor expression and regulatory phosphorylation events will also be determined. Aim 2 will investigate the discrete second messenger pathways and transcription factors that are required for FGF- 1- and SF/HGF-mediated neuroprotection against hypoxic/ischemic injury. We will use complementary in vitro and neonatal rat hypoxia/ischemia models to examine if specific second messengers and transcriptional regulators primarily downstream of principal investigator3-kinase/Akt signaling pathway mediate FGF- 1 and SF/HGF protection. We will focus on the roles of glycogen synthase kinase-3 alpha/beta (GSK-3alpha/beta), hypoxia inducible factor-1 (HIF-1) and nuclear factor-KappaB (NF-KappaB). In Aim 3 we will determine the role of regulators of the apoptotic cascade in hypoxic/ischemic neonatal brain injury and their involvement in the neuroprotective actions of FGF-1 and SF/HGF. Complementary in vitro and in vivo models will be used to focus on the caspase cascade and its target PARP. Regulators of the caspase cascade such as inhibitors of apoptosis proteins (IAPs) and secondary mitochondria-derived caspase activator (SMAC) will be examined. Results of these experiments in conjunction with those of Aim 2 will allow us to elucidate the antiapoptotic molecular mediators and their regulation by specific second messengers and transcription factors involved in neuroprotection by FGF-1 and SF/HGF against neonatal hypoxic/ischemic brain injury. Experiments outlined in this proposal will identify the specific molecular mechanism by which neuroprotective growth factors protect against hypoxic/ischemic injury in neonatal brain. Our findings will contribute to the development of therapeutic strategies for treating hypoxic ischemic neonatal brain injury.